1. Technical Field
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus including a piezoelectric element.
2. Related Art
As a liquid ejecting head, here is an ink jet type recording head provided with piezoelectric elements that includes a first electrode, a piezoelectric layer and a second electrode on one surface of the flow channel forming substrate in which a pressure generation chamber linking with a nozzle opening is provided. The ink jet type recording head generates pressure change in the pressure generation chamber by means of a driving force of the piezoelectric elements so that ink droplets are ejected from the nozzle opening. There is a problem in that piezoelectric elements, which are used in such an ink jet type recording head, are easily broken due to the external environment, such as humidity or the like. In order to solve this problem, for example, the second electrode is configured to cover the outer circumferential surface of the piezoelectric layer (for example, see JP-A-2005-88441). The first electrode is a common electrode and the second electrode is an individual electrode in JP-A-2005-88441.
Also, an ink jet type recording head is suggested wherein a first electrode of the piezoelectric element is provided in each of the pressure generation chambers as an individual electrode and a second electrode is continuously provided in a plurality of pressure generation chambers as a common electrode (for example, see FIGS. 2 and 4 of JP-A-2009-172878). According to the configuration, the second electrode itself serves as a protective film of a surface section of the piezoelectric layer so that there is no necessity to separately provide a protective film.
In the piezoelectric element in which the second electrode is the common electrode as shown in FIGS. 2 and 4 of JP-A-2009-172878, for example, in a piezoelectric body section in which one of the upper and lower side electrodes is not present, because there is no electron supply source (electrode) that shields a polarization electric charge that is induced on a piezoelectric body surface by a stress deformation, an instance of insulation damage or cracking readily occurs due to the induced polarization electric charge.
The above-described problem is present not only in the ink jet type recording head but also in the liquid ejecting head ejecting liquids other than ink.